Adhesive fluoride varnish

ABSTRACT

The invention relates to mixtures comprising polymers containing hydrogen-siloxane groups and fluoride, in addition to the use of said mixtures as a dental scaling varnish and fluoridation varnish and as a desensitising agent, in addition to the use of said mixtures as a protective covering for glasionomer cement fillings.

This application is a 371 of PCT/EP01/09072 filed on Aug. 6, 2001,published on Feb. 14, 2002 under publication number WO 02/1 1681 A1which claims priority benefits from German patent application number DE100 39 298.9 filed Aug. 7, 2000 and German patent application number DE10040716.1 filed Aug. 17, 2000.

This invention relates to mixtures containing polymers havinghydrogen-siloxane groups and fluorides as well as their use as a dentalsealing varnish and fluoridation varnish, a desensitizing agent and aprotective varnish for glass ionomer cement fillings.

Protective varnishes for teeth have been in use successfully for almostthree decades. First, there are the fissure-sealing varnishes based onphotopolymerizable (single component) or self-polymerizing(dual-component) methacrylate resins. Their use requires priorsuperficial etching of the enamel surface with phosphoric acid. Adhesionto dentin is micromechanical and the protective coating seals themicrofissures for a period of years. In some formulations, the varnishcontains such additives as fluoride salts, a glass powder that releasesfluoride or organic fluoride compounds. Traditional examples includeDelton (Dentsply, USA), Visio-Seal (Espe, Germany).

Secondly, there are fluoride varnishes for teeth, polymer solutionscontaining fluorides which leave behind a colorless protective filmresembling nail polish on the surface of the tooth after evaporation ofthe solvent. Films of this type remain on the surface of the tooth foronly a short period of time and are used only as a depot for thefluoride to be administered. Examples of this group of fluoridevarnishes include products such as Bifluorid (Voco, Germany) andDuraphat (Colgate, Germany).

Adducts of silicones and acid-containing monomers constitute anotherdevelopment in the field of dental varnishes (K. G. Bohlig et al.,abstract 1036, J. Dent. Research, vol. 79, Spec. Issue 2000). In thiscase, polymers containing fragments of silicone with SiOH and —COOHgroups are applied in the form of a solution to the dental surface.Their dual functionality makes it possible for them to adhere to theenamel surface without superficial etching (—COOH) as well as to undergoself-crosslinking in the presence of potential condensation catalystsand crosslinking agents (SiOSiOH+Si(OR)₄+HOSiOSi---->SiOSiO—OSiO—SiOSi). Varnishes of this type are more hydrophobicthan those in the past and therefore are less easily washed out, adherewell and are quite durable when crosslinked.

PCT/EP 0001042 and European Patent 0 632 060 A1 describe adhesives ofcopolymers containing hydrogen-siloxane groups and solutions thereof.Adhesives according to PCT/EP 0001042 unexpectedly also adhere to toothenamel.

The objéct of the present invention was to discover a neutral varnishwhich would be capable of forming an adhering, potentially crosslinkingdental coating and could serve as a carrier for fluoridation agents.

According to this invention, this object has been achieved throughmixtures containing

-   -   a) polymers having hydrogen-siloxane groups,    -   b) fluorides,    -   c) optionally a platinum catalyst, and    -   d) optionally vinyl compounds.

The mixtures according to this invention contain polymers havinghydrogen-siloxane groups as an important substance which forms a varnishthat adheres to dental substance. The basic structure of these polymersmay be, for example, copolymers of methyl methacrylate and allylmethacrylate with hydrogen-siloxane grafted onto them. They may also becopolymers such as those described in detail in European Patent 0 632060 A1 or, especially preferably, copolymers obtained by directpolymerization of hydrogen-siloxanes, as described in the attachedPCT/EP 0001042 and in Unexamined Japanese Patent Specification (A) No.HEI 10-25322 published on Jan. 27, 1998. With respect to the(co)polymers and their production, explicit reference is made to thethree publications cited above. The SiH groups of the hydrogen-siloxaneunits are evidently capable of reacting with the POH groups of apatitedental substance so that bonding of the varnish to dental substancecomes about by a chemical route without prior mechanical roughening(etching).

The fluorides that are used may be the same as those contained inconventional commercial fluoride varnishes. Fluorides used in many casesare organic or inorganic fluorides such as sodium fluoride, potassiumfluoride, calcium fluoride, strontium fluoride, zinc fluoride, tinfluoride, sodium or potassium hexafluorophosphate, sodium or potassiumhexafluoroaluminate, ammonium fluoride or organic fluorides such asamine fluorides, e.g., cetylamine hydrofluoride,bis(hydroxyethyl)aminopropyl-N-hydroxyethyloctadecylaminedihydrofluoride.

According to this invention, solid fluorides may be ground to the finestpossible particle size, e.g., to an average particle size between 1 and10 microns or dissolved in one of the solvents mentioned below.

Liquid fluorides may be used as such or dissolved in one of the solventslisted below.

The mixtures according to this invention preferably contain the polymershaving hydrogen-siloxane groups and fluorides in a weight ratio of 100:1to 10:5, especially preferably in a weight ratio of 20:1 to 10:4.

In addition, they may contain up to 10 parts by weight, preferably up to1 part by weight of a vinyl compound, up to 500 ppm, preferably up to 50ppm platinum catalyst and up to 80 parts by weight, preferably up to 20parts by weight polymer(s) without hydrogen-siloxane groups.

The SiH groups of the hydrogen-siloxane units of the polymers usedaccording to this invention have a tendency to undergo hydrolysis in ahumid or moist medium (SiH ---->SiOH), and they tend to crosslink andsplit off hydrogen (SiH+SiOH ---->SiOSi+H₂). In the oral medium, thiscleavage of hydrogen takes place after application of the dentalvarnish, thus leading to a subsequent crosslinking. Thus, a catalyst isnot absolutely necessary.

If it is desirable to achieve rapid crosslinking of the varnishpolymers, especially in the presence of vinyl compounds or othercompounds containing double bonds, then it may be beneficial to add acatalyst, if necessary, capable of catalyzing the SiH+SiOH reaction orthe SiH+—CR═CR₂ reaction. These catalysts are known to be compounds ofplatinum or palladium as well as alloys thereof. Platinum(0) compoundsproduced by starting with platinum hexachloroplatinate are especiallysuitable; these compounds are conventionally used inaddition-crosslinking vinyl-polysiloxane/hydrogen-polysiloxane systems.

Examples of such catalysts include: PT_(x)(divinyltetramethyldisiloxane)_(y) of platinum(0).

optionally added vinyl compounds should preferably be divinyl compounds.However, compounds with more than two vinyl groups may also beappropriate, e.g., when a higher degree of crosslinking is to beachieved. Preferred divinyl compounds include divinyl ethers such as thedivinyl ether of triethylene glycol or cyclohexanediol ordivinylpolysiloxanes such as those used in addition-crosslinkingsilicones or divinyltetramethyldisiloxane.

Mixtures according to this invention may additionally also containpolymers which do not have any SiH groups. Examples of these includepolymethacrylates, polycarbonates, polyesters and similar polymers, ifthey are soluble in the mixture and are compatible with the system.

Likewise, mixtures according to this invention may contain solvents,preferably readily volatile solvents which make it possible to apply thevarnish as a very thin film. Suitable solvents include especiallyreadily volatile inert solvents such as halogenated or non-halogenatedaliphatic or aromatic hydrocarbons, ethers, ketones, esters or cyclicsiloxanes. In particular, physiologically safe solvents may also be usedand especially preferably solvents in which the soluble fluorides usedaccording to this invention are readily soluble.

For stabilization of insoluble fluoride powder particles, additives maybe added to the mixtures according to this invention to counteractpremature separation. Such substances may include for example pyrogenicsilicas or modified cellulose. Additives in the form of agents toprevent caking of deposited particles may also be appropriate andindicated when the mixtures are to be stored for a long period of timeand should be rehomogenizable by shaking gently. Compounds or agentshaving biostatic, biocidal or pharmaceutical effects such asantibacterial or anti-inflammatory effects may also be added. Biocidalcompounds or agents are those which kill bacteria, viruses and/or fungi,while biostatic compounds or agents inhibit the growth of bacteria,viruses and/or fungi.

According to another embodiment, the mixtures according to thisinvention may also contain hydrogen-siloxanes different from thoseaccording to a). Such hydrogen-siloxanes are preferably polysiloxaneshaving at least two SiH groups, preferably three SiH groups.

Due to the presence of phosphoric acid, mixtures according to thisinvention are excellently suited for use as adhesive dental varnishesfor sealing fissures without requiring etching by phosphoric acid. Dueto the lack of etching, it is possible to prevent damage to healthydental enamel beyond the sealing area, while on the other hand there areno unetched non-bonding surfaces beneath the sealing. Another majoradvantage is the fact that sealing with varnishes according to thisinvention can be supplemented easily, but this is not possible on suchan intimate basis with fissure sealing materials based on methacrylate.Another advantage is that sealing according to this invention can beperformed in an extremely thin layer, which is not possible withmethacrylate sealing because of the 50-100 micron-thick inhibition layerdue to the presence of atmospheric oxygen.

Also as an adhesive varnish for fluoridation of dentin, the varnishesaccording to this invention are superior to the fluoridation varnishesused in the past. They adhere chemically, i.e., much better, are morehydrophobic, are stable for several months even on load-bearing surfacesand can easily be supplemented at any time.

Mixtures according to this invention are also suitable fordesensitization of the neck of the tooth. When applied, they rapidlyseal open channels in the dental enamel after the solvent has evaporatedand thus prevent the painful symptoms.

It has unexpectedly also been found that varnishes according to thisinvention are also excellently suited as protective varnishes forcements such as dental cement. For example, the surface of freshlyprepared glass ionomer cement applied as a filling must be provided witha protective varnish. In the past, protective varnishes of this typehave been solutions of polymers such as polymethyl methacrylates,polyesters, polycarbonates or the like. These varnishes remain on thesurface of the fresh cement filling for only a few hours or days; theyadhere only mechanically and are washed away quickly. Although they dolargely fulfill their function because the glass ionomer cements mustmainly be protected in the first minutes to hours, namely until thehardening mechanism has led to structures which are less soluble andhave three-dimensional crosslinking, nevertheless the varnishesaccording to this invention have the advantage that, first of all, theyare more hydrophobic and thus they are better in preventing theunderlying layers of cement from dissolving away; secondly, the fluoridecontent of the varnishes according to this invention protects andsupplements the fluoride reservoir of the glass ionomer cement and thusprolongs its efficacy. Subsequent application of varnishes according tothis invention to glass ionomer fillings may also lead to a “recharging”of fluoride in the glass ionomer filling, which is known to be possiblewith fluoride applications and which can take place intensely andpermanently due to the prolonged presence of the varnish according tothis invention on the glass ionomer surface.

All the quantity amounts given below are based on weight, unlessotherwise indicated.

EXAMPLES Example 1

Fissure Sealing Material

A copolymer containing hydrogen-siloxane was produced according toexample 1 of PCT/EP 00/01042. A mixture according to this invention wasprepared fresh from 10 parts of the polymer, 2 parts extremely finelyground sodium fluoride, 0.2 parts ethylcellulose, 0.05 parts titaniumdioxide and 57 parts ethyl acetate. After brief but intense mechanicalcleaning with a rotating brush with polish paste, cleaning with ethanoland subsequent rinsing with water, drying with oil-free air, thefissures of the occlusive surface of a deciduous molar tooth was coatedtwice with a thin layer of the solution using a dental brush. Aftereight weeks, the sealing was still visible.

Example 2

Antiplaque Fluoride Varnish

A mixture according to this invention was prepared fresh from 10 partsof the polymer from example 1, 0.2 parts extremely finely ground zincfluoride, 0.1 parts Aerosil 810 (Degussa), 89 parts ethyl acetate. Aftera brief but intense mechanical cleaning with a rotating brush usingpolish paste, cleaning with ethanol and subsequent rinsing with water,drying with oil-free air, the labial surface of a front tooth was coatedonce with a thin layer of the solution using a dental brush. After 8weeks, the tooth was checked for plaque with the help of a plaquestaining test. No plaque could be detected on the surface treatedaccording to this invention whereas all the other teeth had more or lesspronounced plaque phenomena.

Example 3

Desensitizer

The solution from example 2 was placed on the neck of a sensitive toothafter appropriate pre-cleaning. After a brief period of time, thesensitivity had disappeared. After eight weeks, the thin layer offluoride varnish was still discernible.

Example 4

Cement Varnish

A copolymer containing hydrogen-siloxane was prepared according toexample 1 of PCT/EP 00/01042. A mixture according to this invention wasprepared fresh from 12 parts of the polymer (see example 1), 1 partextremely finely ground sodium fluoride, 0.1 part ethylcellulose and 90parts methyl ethyl ketone. A test body was produced from freshlyprepared glass ionomer cement (Aqua Ionofil Plus, Voco, Germany), thesurface was coated with the varnish according to this invention and thesample was placed immediately in water. The same procedure was repeated,but this time without treating the surface according to this invention.After one week, the samples were removed from the water. The surface ofthe test body treated according to this invention was much smoother andmore scratch-resistant than the untreated test body.

1. A method of adhering a varnish to teeth or cement fillings, comprising adhering to the teeth or cement filings a mixture containing: a. polymers with hydrogen-siloxane groups; b. fluorides, c. optionally a platinum catalyst, d. optionally vinyl compounds, wherein (a) are copolymers of unsaturated compounds onto which siloxanes containing SiH groups have been grafted; and wherein the mixture is a varnish comprising a sealing varnish for teeth, a fluoridation varnish, a neck desensitizer, a protective varnish for cement, and/or a protective varnish for dental cement.
 2. The method according to claim 1, wherein the fluorides are inorganic fluorides such as sodium fluoride, potassium fluoride, calcium fluoride, strontium fluoride, zinc fluoride, tin fluoride, hexafluorophosphates, or amine fluorides.
 3. The method according to claim 1, wherein the platinum catalyst is a compound of platinum (0).
 4. The method according to claim 1, wherein the vinyl compounds have vinylsiloxane groups or vinyl ether groups.
 5. The method according to claim 1, wherein the mixture also contains polymers without hydrogen-siloxane groups.
 6. The method according to claim 1, wherein the mixture also contains readily volatile solvents.
 7. The method according to claim 1, wherein the mixture also contains compounds or agents having a biostatic, biocidal or other pharmaceutical effect.
 8. The method according to claim 1, wherein the mixture also contains hydrogen-siloxanes other than those according to (a).
 9. A method of adhering a varnish to teeth or cement fillings, comprising adhering to the teeth or cement fillings a mixture containing: a. polymers with hydrogen-siloxane groups; b. fluorides; c. optionally a platinum catalyst; d optionally vinyl compounds; wherein (a) are copolymers of SiH groups-containing siloxanes with unsaturated compounds, and wherein the mixture is a varnish comprising a sealing varnish for teeth, a fluoridation varnish, a neck desensitizer, a protective varnish for cement, and/or a protective varnish for dental cement.
 10. The method according to claim 9, wherein the fluorides are inorganic fluorides such as sodium fluoride, potassium fluoride, calcium fluoride, strontium fluoride, zinc fluoride, tin fluoride, hexafluorophosphates, or amine fluorides.
 11. The method according to claim 9, wherein the platinum catalyst is a compound of platinum (0).
 12. The method according to claim 9, wherein the vinyl compounds have vinylsiloxane groups or vinyl ether groups.
 13. The method according to claim 9, wherein the mixture also contains polymers without hydrogen-siloxane groups.
 14. The method according to claim 9, wherein the mixture also contains readily volatile solvents.
 15. The method according to claim 9, wherein the mixture also contains compounds or agents having a biostatic, biocidal or other pharmaceutical effect.
 16. The method according to claim 9, wherein the mixture also contains hydrogen siloxanes other than those according to (a). 